Color electrophotography using a photoconductive layer on both sides of a multicolor screen

ABSTRACT

A novel electrophotographic reproduction process for producing a plurality of multicolor prints from a single exposure of a color original. The process makes use of a novel color electrophotograhpic recording element which preferably comprises a pair of pan-sensitive photoconductive layers, each having a conductive electrode in electrical contact therewith, and a multicolor additive filter mosaic which is sandwiched between the conductive electrodes of the photoconductive layers during the reproduction process.

United States Patent 1191 1111 3,836,363 Plutchak Sept. 17, 1974 COLORELECTROPHOTOGRAPHY USING 3,413,117 11/1968 Gaynor 96/1.2

A PHOTOCONDUCTIVE LAYER ON BOTH 3,458,309 7/1969 Gaynor 96/ 1.2

SIDES OF A MULTICOLOR SCREEN Inventor: Thomas Miles Plutchak, Webster,

Assignee: Eastman Kodak Company,

Rochester, NY.

Filedz Dec. 26, 1972 Appl. No.: 318,352

References Cited UNITED STATES PATENTS 6/1964 Land 96/80 X 12/1965Tokumoto 96/l.24

ABSTRACT A novel electrophotographic reproduction process for producinga plurality of multicolor prints from a single exposure of a colororiginal. The process makes use of a novel color electrophotograhpicrecording element which preferably comprises a pair of pan-sensitivephotoconductive layers, each having a conductive electrode in electricalcontact therewith, and a multicolor additive filter mosaic which issandwiched between the conductive electrodes of the photoconductivelayers during the reproduction process.

14 Claims, 12 Drawing Figures PATENTEDSEPIYIQM Y 3.836.363

SHEEI S (If 5 COLOR ELECTROPHOTOGRAPHY USING A PI-IOTOCONDUCTIVE LAYERON BOTH SIDES OF A MULTICOLOR SCREEN BACKGROUND OF THE INVENTION Thepresent invention relates to color electrophotography and particularlyto a process for making multiple color prints from a single exposure ofa color original. It also relates to a novel recording element useful incolor electrophotography.

Various electrophotographic color processes have been proposed formaking color prints from a color original. See, for instance, theprocesses disclosed in R. M. Schafferts texton Electrophotography, FocalPress 1965, as well as the processes disclosed in US. Pats. Nos.3,057,720; 3,150,976; 2,940,847; and 3,212,887. All of the processesdisclosed in the above references, however, lack the capability ofproducing multiple fullcolor prints of a colored original from a singleexposure of such original. All require that the electrophotographicrecording element be imagewise exposed each time a color print isproduced. This exposure requirement not only adversely affects the rateat which multiple prints can be produced, it also renders the originalinaccessible until all prints have been made. Moreover, all of theseprocesses involve multiple imagewise exposures of the recording element,which exposures must be precisely in registration in order for goodquality prints to be made.

SUMMARY OF THE INVENTION It is, therefore, an important object of thepresent invention to provide an electrophotographic process in which amultitude of color prints can be made from an electrophotographicrecording element which has been imagewise exposed only once to thecolor original.

It is another object of this invention to produce positive-appearingcolor prints from either positiveor negative-appearing originals.

Another object of the invention is to provide a novelelectrophotographic process for making color prints of multicolororiginals which process does not require the registration of multipleimagewise exposures which is characteristic of prior art methods.

Still another object of the invention is to provide a novel method ofmaking color prints ofa color original electrophotographically.

A further object of the invention is to provide novel recording elementsuseful in the color electrophotographic process of the invention.

In accordance with the present invention, a novel electrophotographicrecording element comprising a multicolor additive filter mosaicsandwiched between two photoconductive layers is utilized in carryingout the novel electrophotographic color process. At least one of thephotoconductive layers of the recording element is substantiallytransparent to the visible or optical region of the electromagneticspectrum, and each has an electrode or conductive layer in electricalcontact'therewith. The mosaic is disposed between the respectiveelectrodes of the photoconductive layers, and is laterally divided intoa multitude of color filter elements which are constructed to effectselective transmission of predetermined portions of the visibleelectromagnetic spectrum substantially corresponding to its red, green,and blue regions. The photoconductive layers are spectrally sensitive atleast to the colors transmitted by the various filter elements of themosaic and preferably are pan-sensitive (i.e., sensitive to all visibleelectromagnetic radiation.)

To carry out the novel process, one photoconductive layer of therecording element is uniformly charged and imagewise exposed to a colororiginal through the mosaic. The resulting electrostatic latent image isdeveloped with an opaque electrographic toner. The other photoconductivelayer is then uniformly charged, exposed, and developed three successivetimes, using red, green, and blue light to expose, and cyan, magenta,and yellow electrographic developer, respectively. The last threeexposures are made through the opaque toner image-bearing surface of thefirst photoconductive layer and the mosaic. The resulting color image isthen transferred to a receiver sheet. Multiple color prints of the colororiginal can then be made with no additional exposure to the original bymerely cleaning the residue of untransferred color developer, leavingthe black toner image undisturbed, repeating the three successive cyclesof uniform charging, exposing and color developing, and transferring thecolor image to a receiver sheet.

Various other objects of the invention, as well as its advantages, willbecome apparent to those skilled in the art from the ensuing detaileddescription of preferred embodiments, reference being made to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross section of a colorelectrophotographic recording element useful in carrying out the novelprocess of the invention;

FIGS. 2 (a) through 2 (h) schematically illustrate the sequential stepsof the inventive process;

FIGS. 3 and 4 illustrate various other forms which the novel recordingelement of the invention may take; and

FIG. 5 illustrates an automatic electrophotographic apparatus forcarrying out the inventive process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A novelelectrophotographic recording element 10 suitable for use in producingcolor prints in accordance with the present invention is illustrated inFIG. 1. As

shown, recording element 10 comprises a trichromatic filter mosaic 11which is sandwiched between the conductive coatings 12 and 12 (a) of apair of pan-sensitive photoconductive layers 13 and 14, respectively.The conductive coatings, as well as their respective photoconductivelayers, are substantially transparent to the visible portion of theelectromagnetic spectrum. Preferably, each photoconductive layer isapproximately ten microns thick and comprises an aggregated organicphotoconductor containing 4,-4-diethylamino-2,2-dimethyltriphenylmethane as the organic photoconductor, a polycarbonatebinder such as Lexan (a General Electric Company trade name), and 4-(4-dimethylaminophenyl)-2,o-dilphenylthiapyrylium fluoroborate and4-(4-dimethylaminophenyl)-2-(4- ethoxyphenyl)-6-phenylthiapyryliumfluoroborate as sensitizer dyes.

Mosaic 11 preferably comprises a transparent support 15 having atrichromatic layer '16 disposed thereon. Trichromatic layer 16 islaterally divided into a multitude of additive color filter elements, R,G, and

B. which correspond to red, green, and blue filter elements,respectively. Such filter elements are contiguously arranged and maytake the forms of minute dots, squares, triangles, or other geometricconfigurations, or, alternatively, be in the form of narrow lines (e.g.,0.002 inch in width) which extend in one dimension across the entirerecording element. Preferably, the colored portions are orderly arrangedto the extend that, for any given area, the number of red, green, andblue portions will be substantially equal. Red filter element R isconstructed to be selectively transparent to the red region of thevisible spectrum, being relatively opaque to the blue and green regions.Similarly, green filter element G transmits a high percentage of greenlight, but relatively little red and blue light, and blue filter elementB transmits a high percentage of blue light, but relatively little redand green light. Mosaic 11 is preferably produced photographically onEastman Color Print Film (a trademark of Eastman Kodak Company) usingmaster grids produced by a scanning apparatus manufactured by K. S. PaulCompany. The polyethylene terephthalate film base serves as support andthe colored filter elements are formed in the emulsion layer of thefilm.

To use the recording element described above to produce color prints,the novel process illustrated schematically in FIGS. 2 (a) through 2 (h)is carried out. As will be noted, the conductive layers 12 and 12 (a)are connected to a reference voltage, preferably ground potential,during the process. The first step of the process is to uniformly chargeone of the photoconductive layers of the recording element, layer 13,for instance, to several hundred volts. For purposes of illustration,the uniform charge is shown to be of a positive polarity. Such uniformcharging can be accomplished, for instance, by advancing the recordingelement at a uniform rate in close proximity to a conventional coronacharging unit. The uniformly charged photoconductive layer 13 is thenimagewise exposed to the color original. White light, such as providedby a xenon lamp, is used to illuminate the original and imagewiseexposure of layer 13 is effected through the color mosaic and the otherphotoconductive layer (i.e., layer 14). The effects of such exposure areillustrated in FIG. 2 (a) wherein the charge-dissipating effects ofvarious colors comprising the color original are shown. As illustrated,the red portions of the color original serve to dissipate charge on theuniformly charged photoconductor only in those areas opposite the redfilter elements of the mosaic. Such charge dissipation is, of course,effected due to the increase in conductivity of the photoconductivelayer 13 with exposure, and by the connection of conductive layer 12 toa lower potential (ground) than that corresponding to the initialcharge. Similarly, charge is dissipated from the uniformly chargedphotoconductor by the green portion of the color original only in thoseareas opposite the green filter elements of the mosaic. When theuniformly charged photoconductive layer is exposed, through the mosaic,to cyan light, charge is dissipated in those areas opposite both thegreen and blue filter elements of the mosaic, since cyan has green andblue components. In those areas where no light strikes thephotoconductor, the uniform charge, of course, remains unaltered. Wherewhite light strikes the uniformly charged photoconductive surfacethrough the mosaic, the charge is dissipated uniformly from layer 13 inall exposed areas.

Upon being imagewise exposed to the color original, through the mosaic11, those areas of the photoconductor where charge was dissipated aredeveloped with a black or opaque electrographic toner. See FIG. 2 (b).Such development can be effected by any of the wellknown electrographicdevelopment techniques (i.e., cascade, liquid, magnetic brush, etc.,development) using positively charged electroscopic toner. Followingsuch development, photoconductive layer 14 is successively uniformlycharged and flood exposed to the three additive colors of the recordingelement mosaic. The sequence or order of the colored flood exposures isimmaterial. Following each charge and exposure step, a different coloredelectrographic developer is applied to the resulting electrostaticimage, the particular color of such developer being predominantlyspectrallyabsorptive of the exposing color preceding such development.For instance, as shown in FIG. 2 (c), upon forming a black toner imageon photoconductive layer 13 of the recording element, photoconductivelayer 14 is uniformly charged (e.g., by a corona charger) and floodexposed, through the color mosaic, to red light. See FIG. 2 (c). Inthose areas of the uniformly charged photoconductive layer 14 oppositethe red filter elements of the mosaic which are exposed to the redlight, the uniform charge is dissipated. Note charge on some areas oflayer 14 opposite the red filter elements of the mosaic will not bedissipated; these areas correspond to those areas shielded from exposureto red light by the black toner image previously formed on layer 13.Since red light is absorbed by the blue and green filter elements of themosaic, charge on the photoconductive surface of layer 14 opposite thesefilter elements remain also. The resulting electrostatic image is thendeveloped with a cyan colored electrographic toner c, (cyan beingpredominantly spectrally absorptive of red light and transmissive ofother colors), producing the result schematically illustrated in FIG. 2(d). Note, as shown in the drawings, color toner development is effectedonly in those areas on the photoconductive surface where charge isdissipated.

Next, photoconductive layer 14 bearing the cyan colored toner particlesis uniformly charged and flood exposed to green light. Again, floodexposure is effected through the mosaic and the black toner-bearingphotoconductive layer of the recording element. See FIG. 2 (e). Upondeveloping those areas in which charge is dissipated, with a magentacolored electrographic developer M, the result is as illustrated in FIG.2 (f).

Finally, photoconductive layer 14, hearing the cyan and magenta coloredtoner particles, is uniformly charged and flood exposed, through themosaic and layer 13 to blue light. See FIG. 2 (g). Upon developing thoseareas in which charge is dissipated with a yellow electrographicdeveloper Y, a full color print 19 of the original is provided on therecording element surface. This color image can then beelectrostatically transferred to a paper receiving sheet and fixedthereon, permitting the recording element to be recycled through theprocess steps illustrated in FIGS. 2 (c) 2 (h) to produce multiple colorprints.

The operability of the process described above is illustrated by thefollowing examples in which a color print comprised of two of the threeprimary additive colors, red and blue, is produced.

EXAMPLE 1 A bichromatic filter mosaic was made photographically onEastman Color Print Film by repetitively scanexposing the film to redand blue light using the aforementioned K. S. Paul Scanner. This mosaicwas then employed in the recording element illustrated in FIG.

One photoconductive layer of the recording element (e.g., layer 13) wasuniformly and positively charged to approximately 600 volts using aconventional gridcontrolled corona charger. This layer was then contactexposed with white light from a xenon arc source to a color originalthrough the bichromatic mosaic for approximately 20 seconds. Those areasof the photoconductive layer on which charge was dissipated by theexposure to the original were developed with a liquid blackelectrographic developer and rinsed with lsopar G, a Humble Oil Companytrade name for an isopraffinic hydrocarbon using a positive 550 voltsbias on a development electrode and a negative 150 volts bias on therinse electrode. A conductive development elec trode and rinse electrodewere positioned approximately 0.02 inch from the surface of thephotoconductor during the development and rinse steps.

The other photoconductive layer (layer 14 in FIG. 1) was then uniformlycharged to a positive polarity of approximately 600 volts, using agrid-controlled charger. This layer was subsequently flooded uniformlywith red light through the black toner deposit on layer 13 and themosaic for approximately 50 seconds. The areas that were discharged bythe red light flood exposure were then developed with a cyan coloredliquid electrographic developer and rinsed with lsopar G using apositive 550 volts bias on the development electrode and a negative 150volts bias on the rinse electrode. Layer 14 was then uniformly charged,flood exposed, and developed a second time in exactly the same manner asthe first time, except that this time a blue light flooding exposure ofabout 100 seconds duration and a yellow developer were used. The bluelight was obtained by modulating a xenon are light source with adichroic cut-off filter which effectively blocked wavelengths longerthan about 677 nanometers and a Wratten Filter 478 (an Eastman KodakCompany trade name). The red light used for the uniform floodingexposure was obtained by modulating the xenon arc source with a dichroiccut-off filter which effectively blocked wavelengths longer than about725 nanometers and a Kodak Wrattan Filter 70.

The resulting two-color image was transferred to a receiver sheet whileit was moist by rolling the receiver sheet into contact with the imageusing a conducting rubber roller that was electrically biased toapproximately minus 1,000 volts. The receiver in this case was aclay-coated paper which had been made conductive and which had beengiven a thin (approximately 5- micron) insulating coating of polyvinylbutyral resin and titanium oxide particles. The resulting print was atwo-color reproduction of the original containing green, cyan, yellow,and white areas corresponding to black, blue, yellow, and white areas,respectively, in the original. The print was lacquered with a solutioncontaining a clear styrene-butadiene polymer to protect it and to give aglossy finish. This process demonstrated the production of positivecolor prints from a positive color original.

EXAMPLE 2 Photoconductive layer 14 used in Example 1 was cleaned, butthe black toner deposit on photoconductive layer 13 was leftundisturbed. The operations performed on layer 14 in Example l were thenrepeated. The resulting two-color image was then transferred andlacquered to produce a second color print which was identical to thefirst.

This process was repeated two more times to produce a total of threeadditional color reproductions of the original with no further exposureto the original. Although only three additional color reproductions weremade, it was apparent that any desired number of additional colorreproductions could have been made with no further exposure to theoriginal and with each additional color reproduction being identical tothe first.

EXAMPLE 3 Photoconductive layer 14 of the recording element used inExamples I and 2 was cleaned, but the black toner deposit onphotoconductive layer 13 was left undisturbed. Layer 14 was thenuniformly charged, floor exposed with red through the black image onlayer 13 and the mosaic, developed with cyan developer, and rinsed as inExample l, except that the development electrode bias and the rinseelectrode bias were both positive 550 volts; consequently, during thedevelopment and rinse steps, layer 14 recharged to approximatelypositive 550 volts. Layer 14 was then flood exposed using blue lightthrough the black image on layer 13 and the mosaic, and developed withyellow developer in the manner described in Example 1, except that bothdevelopment and rinse electrode biases were +500 volts.

The two-color image was transferred and lacquered as in Example 1, andthe resulting print was again a reproduction of the original. Theprocess used in making this print was, however, somewhat simpler thanthe process used in Examples 1 and 2, since in this example, layer 14was recharged during the cyan development step and the associated rinsestep making it possible to omit the subsequent corona charging step.

EXAMPLE 4 Photoconductive layer 13 in FIG. 1 was uniformly charged toapproximately -600 volts using a gridcontrolled corona charger. Layer 13was then contact exposed to the color original through a two-colormosaic (red and blue) for approximately seconds using white light thatwas modulated with a Kodak Wratten Filter 28 and a dichroic cut-offfilter that effectively blocked wave-lengths longer than about 725nanometers. Those areas of layer 13 that were not discharged by theexposure to the original were developed with black electrographicdeveloper and rinsed with lsopar G, using a --75 volt bias on thedevelopment electrode and a 775 volt bias on the rinse electrode.

Two cycles of uniform charging, flood exposing, and developing wereperformed on layer 14 in the same manner as in Example 1, except thatthe red flooding exposure was for approximately 25 seconds and the blueflooding exposure was for approximately seconds and was made using aKodak Wratten Filter 50.

The two-color image was then transferred to a receiver sheet andlacquered in the same manner as in Example 1. The resulting print was atwo-color, negative-to-positive reproduction of the color originalcontaining green, cyan, yellow and white areas corresponding to white,red, blue and black areas, respectively.

EXAMPLE Photoconductive layer 14 of the recording element illustrated inFIG. 1 and used in Example 4 was cleaned, with the'black toner depositon layer 13 was left undisturbed. Two cycles of uniform charging, floodexposing and developing were then performed on layer 14 in the samemanner as in Example 4.

The two-color image was then transferred to a receiver sheet in themanner described in Example 1, but inthis case the receiver sheet wasbond paper which had been pre-wet with lsopar G. The transfer wasessentially complete and the resulting print was a negative-to-positivereproduction of the original.

EXAMPLE 6 The operations described in Example 5 were repeated, but inthis example dry bond paper was used as the receiver sheet. The transferwas very good, although not as complete as in Example 5, and theresulting print was again va negative-to-positive reproduction of theoriginal.

Although the examples above illustrate a two-color system, the extensionto a full-color system is straightforward. lt merely requires that themosaic have green filter elements as well as red and-blue filterelements, and it requires that an additional cycle of uniform charging,green uniform flooding exposure, and magenta development be performed.

The method used in making each of the developers used in the above,examples is to disperse a small amount of an appropriately coloredconcentrate into a isoparaffinic hydrocarbon, such as Isopar G (aGeneral Electric tradename). Each of the developers, therefore, isbasically a suspension of the color concentration in a isoparaffinichydrocarbon. The black concentrate comprised carbon black, such as CabotELF-O (a Cabot Corporation tradename), and Monsastral Blue (a DuPonttrade name) pigment as colorants in cyclohexane, with a soya-modifledalkyd resin, and an oilsoluble phenol-formaldehyde resin as additionalingredients. The cyan concentrate comprised Monastral Blue pigment asthe colorant in Solvesso (a Standard Oil Company trade name for certainhydrocarbon solvents) with a soya-modified alkyd resin, an oil-solublephenol-formaldehyde resin, a small amount of a solution of cobaltnaphthenate containing 6 percent cobalt and a small amount of aluminumstearate as additional ingredients. The yellow concentrate can have thesame formulation as the cyan concentrate, except that the colorant isPermanent Yellow HR (an American Hoechst trade name) pigment, and noUversol Cobalt Liquid is used. A magenta concentrate can comprise aprecipitate formed from Astraphloxine FF (made by Eastman KodakCompany), phosphotungstic acid and phosphomolybic acid. All of thesedevelopers intrinsically carry a positive charge.

An alternate method of making a positive-to-positive reproduction is tocharge negatively throughout the process and, after each exposure step,develop the areas that were not discharged with the appropriatedeveloper. An alternate method of making a negative-topositivereproduction is to uniformly charge layer 13 to one polarity (e.g.,positive) prior to the imagewise exposure step, and then charge to theopposite polarity (e.g., negative) throughout the remainder of theprocess. The blank development step would then be performed such thatthe areas that were discharged during the exposure to the original wouldbe developed. The cyan, magenta and yellow development steps would beperformed such that the areas that were not discharged during theexposure to the original would be developed.

As indicated in the examples, a variety of receiver sheets may be used.Preferred receiver sheets are baryta paper that has been madeconductive, polyethylene-encased baryta paper that has a conductinglayer on its surface, and specially treated or coated bond papers.

Any mosaic containing appropriately colored filters of sufficientlysmall dimension can be used as the filter mosaic. The ratios of theindividual color filter elements of the mosaic can be altered to suitthe spectralresponse of the photoconductive material comprising therecording element. This technique can be used to compensate for aphotoconductive material that has significantly more sensitivity in someregions of the spectrum than in others.

The photoconductive layer on which the full-color reproduction isfinally formed can be made separable from the other part of therecording element and whiteappearing. In FIG. 3, a two-part recordingelement is depicted, the separable photoconductive portion beingsupported by a transparent support 20. This layer also could then serveas the final support for the print thus eliminating the need to transferto a receiver. As shown in FIG. 4, the recording element can comprisethree separable elements which are brought together during thereproduction process. Preferably, each element has its own supportinglayer (i.e., layers 15,-21, and 22). When using a twoor three-partrecording element, it is not necessary for the second photoconductivelayer to be brought into position until after imagewise exposure of thefirst photoconductive layer. Moreover, the second photoconductive layerneed not be optically transparent.

One of the several advantages of the process of this invention is that,unlike color electrophotographic processes requiring multiple imagewiseexposures of the original to produce a single color print, there areinherently no registration problems involved. This simplifies machinedesign and reduces the complications of producing a coloredelectrophotographic print.

Another advantage of this invention is that good color rendition ispossible by merelyoverlapping the subtractively colored tonersany'desired degree. Various techniques can be used to obtain theoverlapping of the subtractively colored toners required for the bestpossible color rendition. One technique for obtaining the desired amountof overlap is to design the recording element and the colored lightflooding sources so that the black toner deposits on the firstphotoconductive layer and the filter mosaic are not imaged sharply onthe second photoconductive layer during the uniform flooding exposures.One way that this unsharp imaging can be accomplished is to use exposuresources for the uniform colored light flooding steps that are physicallybroad and that provide diffuse illumination, and to use in conjunctionwith these exposure sources a sandwichstructure recording element wherethe second photoconductive layer is spaced appropriately far away fromthe first photoconductive layer and the color mosaic. The spacingbetween the photoconductive layers, the distance from the flood exposuresources to the recording element, and the shapes and dimensions of theflood exposure sources is adjusted to give the optimum unsharpness,i.e., the optimum overlap of the colorants, for any color mosaic that isemployed. Another technique that can be used to obtain the desiredoverlapping of the colorants would be to introduce a certain amount ofsmearing during the transfer step.

Still another advantage of the novel process of the invention is thatone photoconductive recording element can be used without the need forcleaning the photoconductive surface between the production of each ofthe three successive subtractively colored images.

In FIG. 5, apparatus for carrying out the novel process of the inventionautomatically is schematically illustrated. As shown, the novelrecording element 10 has a closed-loop configuration, being in the formof a cylinder 30. The components of the apparatus are best described inconnection with the description of the operation of the apparatus whichfollows.

Cylinder 30 is rotatably mounted by means not shown and is driven in thedirection indicated by the arrow. As cylinder 30 passes the coronacharging station32, a uniform electrostatic charge is laid down onphotoconductive layer 13 of the recording element. Following suchcharging, layer 13 is imagewise exposed to a color original 34 which isadvanced from a supply roll 36 at the same linear rate as that at whichcylinder 30 moves. Original 34 is maintained in contact with the outersurface of photoconductive layer 14 by rollers 38 and 40, and, followingimagewise exposure, is wound upon take-up roll 42. lmagewise exposure iseffected by activating a source of white light 44 (i.e., a source havingthe additive colors of the mosaic 11 present, preferably insubstantially equal amounts). As shown, such imagewise exposure ofphotoconductive layer 13 is effected through the other layers of therecording element, including photoconductive layer 14 and mosaic 11.Such imagewise exposure serves to selectively dissipate the uniformcharge on layer 13, leaving behind a latent electrostatic image.

Upon being imagewise exposed, the electrostatic image-bearing portion oflayer 13 of the recording element is advanced past an electrostaticdevelopment station 46, shown for purposes of illustration as being ofthe magnetic brush variety, where an opaque or black toner isselectively applied to the surface of layer 13. By properly controllingthe electrical potential of the brush and the polarity of the tonerparticles, either the background or image areas of the electrostaticimage are developed.

Following development with opaque toner, the surface of photoconductivelayer 14 is successively uniformly charged, flood exposed and developedthree times by corona charging stations 50, 52, and 54, flood exposurestations 56, 58, and 60, and development stations 62, 64, and 66. Floodexposure stations 56, 58, and 60 comprise sources of right light, greenlight, and blue light, respectively. Development stations 62, 64, and 66are, like development station 46, of the magnetic brush variety,comprising reservoirs containing cyan, magenta and yellow colored tonerparticles, re-

spectively. These stations serve to produce a full-color image on thesurface of layer 14 in precisely the same manner as described above withreference to FIGS. 2 (0) through 2 (h).

The color image formed on layer 14 is then transferred to an appropriatereceiving sheet 68 by a conventional corona transfer station 72.Receiving sheet 68 is advanced from a supply roll 69 to a take-up roll70 along a path which comes into contact with the periphery of cylinder30 at the transfer station. The transferred image is then permanentizedby a roller fusing apparatus 74, and the residue of colored tonerparticles is removed from the surface of layer 14 by a soft fur brush,or the like. To make multiple copies of the same color original, theopaque toner image is left undisturbed and cylinder 30 is repetitivelyrecycled past the various processing stations.

This invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

I claim:

1. A process for producing a multicolored image from a multicoloredoriginal using a recording element comprising (a) a first pan-sensitivephotoconductive layer having an optically transparent, electricallyconductive layer in electrical contact with one surface thereof; (b) asecond pan-sensitive photoconductive layer having an opticallytransparent, electrically conductive layer in electrical contact withone surface thereof; and (c) a multicolored filter mosaic disposedbetween the conductive layers, at least the first photoconductive layerbeing optically transparent and the multicolored mosaic being dividedinto a multitude of color filter elements, some of such filter elementsbeing predominantly transparent to a first additive color, and othersbeing predominantly transparent to a second additive color, said processcomprising the steps of:

a. uniformly charging the first photoconductive layer of the recordingelement;

b. imagewise exposing the first photoconductive layer to themulticolored original, such imagewise exposure being effected throughthe mosaic using an exposure source comprising light of at least saidfirst and second additive colors, thereby forming a first electrostaticimage on the first photoconductive layer in accordance with the image ofthe multicolored original as attenuated by the mosaic;

c. applying a first electroscopic toner to the first electrostatic imageto produce a first toner image on a surface of the first photoconductivelayer, such first electroscopic toner being opaque to the first andsecond additive colors to which the mosaic is transparent;

d. uniformly charging the second photoconductive layer;

e. exposing the second photoconductive layer to light of said firstadditive color, such exposure being effected through the first tonerimage borne by the surface of the first photoconductive layer andthrough the mosaic, thereby selectively dissipating the uniform chargeon the second photoconductive layer in those areas opposite thoseilluminated filter elements of the mosaic which are predominantlytransparent to the first additive color to form a second electrostaticimage;

f. applying a second electroscopic toner to the second electrostaticimage to produce a second toner image on a surface of the secondphotoconductive layer, such second electroscopic toner being of a colorwhich is predominantly spectrally absorptive of said first additivecolor;

g. uniformly charging that surface of the second photoconductive layerbearing the second toner image;

h. exposing the second photoconductive layer to light of said secondadditive color, such exposure being effected through the first tonerimage borne by the surface of the first photoconductive layer andthrough the mosaic, thereby selectively dissipating the uniform chargeon the second photoconductive layer in those areas opposite thoseilluminated filter elements of the mosaic which are predominantlytransparent to the second additive color to form a third electrostaticimage which is superimposed on the second toner image; and

. applying a third electroscopic toner to the third electrostatic imageto produce a third toner image on that surface of the secondphotoconductive layer bearing the second toner image, such thirdelectroscopic toner being of a color which is predominantly spectrallyabsorptive of said second additive color, whereby a multicolored imageis formed ofthe color original, such color image comprising thesuperimposed second and third toner images.

2. The process according to claim 1 wherein some of the filter elementsof the mosaic layer of the recording element are predominantlytransparent to a third additive color and wherein the exposure sourceused in the imagewise exposing step further comprises light of the thirdadditive color to which the mosaic layer is transparent, and saidprocess further comprises the steps of:

j. uniformly charging the second photoconductive layer bearing thesuperimposed second and third toner images;

it. exposing the second photoconductive layer to light of said thirdadditive color, such exposure being effected through the first tonerimage borne by the surface of the first photoconductive layer andthrough the mosaic, thereby selectively dissipating the uniform chargeon the second photoconductive layer in those areas opposite thoseilluminated filter elements of the mosaic layer which are predominantlytransparent to said third additive color to form a fourth electrostaticimage which is superimposed on the second and third toner images; and

. selectively applying a fourth electroscopic toner to the fourthelectrostatic image to produce a third toner image on that surface ofthe second photoconductive layer bearing the superimposed second andthird toner images, such fourth electroscopic toner being of a colorwhich is predominantly spectrally, absorptive of the third additivecolor, whereby a multicolored image is formed of the color original,such multicolored image being comprised of the superimposed second,third, and fourth toner images. 3. The process according to claim 1further comprising the step of transferring the toner image to areceiving member.

4. The process according to claim 2 wherein the first, second, and thirdadditive colors are red, green, and blue; and thecolors of theelectroscopic toners which are applied following the red, green, andblue flood exposures are cyan, magenta, and yellow, respectively.

5. The process according to claim 4 wherein the first, second, third,and fourth toners are applied to those areas on the photoconductivesurfaces where charge is dissipated during the exposure steps.

6. The process according to claim 4 wherein the first, second, third,and fourth toners are applied to those areas on the photoconductivesurfaces where electrostatic charge remains after the exposure steps.

7. The process according to claim 4 wherein the first toner is appliedto those areas on the first photoconductive layer where charge isdissipated during the imagewise exposure step and wherein the second,third and fourth toners are applied to those areas on the secondphotoconductive layer where charge remains after the subsequent exposuresteps, whereby a negative multicolored image is provided on the secondphotoconductive layer.

8. The process according to claim 4 wherein the first toner is appliedto those areas on the first photoconductive layer where charge remainsafter the imagewise exposure step and wherein the second, third andfourth toners are applied to those areas on the second photoconductivelayer where charge is dissipated during the subsequent exposure steps,whereby a negative multicolored image is provided on the secondphotoconductive layer.

9. The process according to claim 4 wherein the first photoconductivelayer is uniformly charged to one polarity prior to being imagewiseexposed to the multicolored original and the second photoconductivelayer is uniformly charged to an opposite polarity each time prior tobeing subsequently exposed.

10. A process for producing a multicolored image from a multicoloredoriginal using a recording element comprising (a) a first pan-sensitivephotoconductive layer having an optically transparent, electricallyconductive layer in electrical contact with one surface thereof, (b) asecond pan-sensitive photoconductive layer having an opticallytransparent, electrically conductive layer in electrical contact withone surface thereof, and (c) a trichromatic additive colored mosaiccomprising red, green, and blue filter elements positioned between theconductive layers of the first and second photoconductive layers, saidprocess comprising the steps of:

a. uniformly charging the first photoconductive layer of the recordingelement;

b. imagewise exposing the first photoconductive layer to themulticolored original, such imagewise exposure being effected throughthe multicolored mosaic using an exposure source comprising a mixture ofred, green, and blue light, thereby forming a first electrostatic imageon the first photoconductive layer in accordance with the image of themulticolored original;

c. selectively applying an opaque electroscopic toner to the firstelectrostatic image-bearing surface of the first photoconductive layerto produce an opaque toner image;

d. successively uniformly charging, exposing, and applying tonerparticles to the second photoconductive layer using red, green, and bluelight to expose followed by the application of cyan, magenta, and yellowcolored electroscopic toner, respectively, such exposures to red, greenand blue light being made through the opaque toner image and themulticolored mosaic.

11. A color electrophotographic recording element comprising:

a. first and second optically transparent, pansensitive photoconductivelayers, each having an optically-transparent conductive layerelectrically associated therewith; and

b. a trichromatic additive multicolored mosaic comprising red, green,and blue filter elements disposed between the conductive layers of thefirst and second photoconductive layers.

12. A separable color electrophotoconductive recording elementcomprising:

a. a first optically transparent, pan-sensitive photoconductive layerhaving an optically transparent electrode in electrical contact with onesurface thereof;

b. a second pan-sensitive photoconductive layer having an opticallytransparent electrode in electrical contact with one surface thereof;and

c. a multicolor additive filter mosaic layer disposed between theelectrodes of the first and second photoconductive layers.

13. A process for producing a multicolored image from a multicoloredoriginal using a multi-layered recording element comprising first andsecond pansensitive, photoconductive layers, each having an opticallytransparent, electrically conductive layer in electrical contact withone surface thereof; and a multicolored filter mosaic disposed betweensuch conductive layers, the conductive layers and the photoconductivelayers being optically transparent, and the multicolored mosaic beingdivided into a multitude of color filter elements, some of such filterelements being predominantly transparent to a first additive color, andothers being predominantly transparent to a second additive color, saidprocess comprising the steps of:

a. uniformly charging the first photoconductive of the recordingelement;

b. imagewise exposing the first photoconductive layer to themulticolored original, such imagewise exposure being effected throughthe mosaic and the second photoconductive layer using an exposure sourcecomprising light of at least said first and second additive colors,thereby forming a first electrostatic image on the first photoconductivelayer in accordance with the image of the multicolored original asattenuated by the mosaic;

. applying a first electroscopic toner to the first electrostatic imageto produce a first toner image on a surface of the first photoconductivelayer, such first electroscopic toner being opaque to the first andsecond additive colors to which the mosaic is transparent;

d. uniformly charging the second photoconductive layer;

e. exposing the second photoconductive layer to light of said firstadditive color, such exposure being effected through the first tonerimage borne by the surface of the first photoconductive layer andthrough the mosaic, thereby selectively dissipating the uniform chargeon the second photoconductive layer in those areas opposite thoseilluminated fillayer ter elements of the mosaic which are predominantlytransparent to the first additive color to h. exposing the secondphotoconductive layer to light of said second additive color, suchexposure being effected through the first toner image borne by thesurface of the first photoconductive layer and through the mosaic,thereby selectively dissipating the uniform charge on the secondphotoconductive layer in those areas opposite those illuminated filterelements of the mosaic which are predominantly transparent to the secondadditive color to form a third electrostatic image which is superimposedon the second toner image; and

. applying a third electroscopic toner to the third electrostatic imageto produce a third toner image on that surface of the secondphotoconductive layer bearing the second toner image, such thirdelectroscopic toner being of a color which is predominantly spectrallyabsorptive of said second additive color, whereby a multicolored imageis formed of the color original, such color image comprising thesuperimposed second and third toner images,

14. A process for producing a multicolored image from a multicoloredoriginal using a separable recording element comprising (a) a firstpan-sensitive, optically transparent photoconductive layer having anelectrically conductive, optically transparent layer in electricalcontact with one surface thereof, (b) a second pan-sensitivephotoconductive layer having an electrically conductive, opticallytransparent layer in electrical contact with one surface thereof, and(c) a multicolored mosaic divided into a multitude of color filterelements, some of such filter elements being predominantly transparentto a first additive color, and others being predominantly transparent toa second additive color, said process comprising the steps of:

a. uniformly charging the first photoconductive layer of the recordingelement;

b. imagewise exposing the first photoconductive layer to themulticolored original, such imagewise exposure being effected throughthe mosaic using an exposure source comprising light of at least saidfirst and second additive colors, thereby forming a first electrostaticimage on the first photoconductive layer in accordance with the image ofthe multicolored original as attenuated by the mosaic;

. applying a first electroscopic toner to the first electroscopic imageto produce a first toner image on a surface of the first photoconductivelayer, such first electroscopic toner being opaque to the first andsecond additive colors to which the mosaic is transparent;

d. uniformly charging the second photoconductive layer;

e. exposing the second photoconductive layer to light of said firstadditive color, such exposure being effected through the first tonerimage borne by th surface of the first photoconductive layer and throughthe mosaic, thereby selectively dissipating the uniform charge on thesecond photoconductive layer in those areas opposite those illuminatedfilter elements of the mosaic which are predominantly transparent to thefirst additive color to form a second electrostatic image;

applying a second electroscopic toner to the second electrostatic imageto produce a second toner image on a surface of the secondphotoconductive layer, such second electroscopic toner being of a colorwhich is predominantly spectrally absorptive of said first additivecolor;

g. uniformly charging that surface of the second photoconductive layerbearing the second toner image;

of said second additive color, such exposure being effected through thefirst toner image borne by the surface of the first photoconductivelayer and through the mosaic, thereby selectively dissipating theuniform charge on the second photoconductive layer in those areasopposite those illuminated filter elements of the mosaic which arepredominantly transparent to the second additive color to form a thirdelectrostatic image which is superimposed on the second toner image; and

applying a third electrostatic toner to the third electrostatic image toproduce a third toner image on that surface of the secondphotoconductive layer bearing the second toner image, such thirdelectroscopic toner being of a color which is predominantly spectrallyabsorptive of said second additive color, whereby a multicolored imageis formed of the color original, such color image comprising thesuperimposed second and third toner images.

P041050 UNITED sTATEs. PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 4 3,83 Dated September Inventofls) Thomas Miles Plutchak It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 3, line 8, the word "extend" should read --extent--.

Column 6, line 23, the word "floor" should read --flood--;

and on 'line 2 4, after "red" the word --light--should be added.

Column 8, line 6 the word "blank" should read --black--.

Column 13, line 16, the word "electrophotoconductive" after "color"should read --electrophotographic--.

Signed and sealed this 8th day of April 19-75.

(SEAL) test. c. MARSHALL DANN RUTH C. I'TASON Commissioner of PatentsArresting Officer and Trademarks gggg UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION mm No. 3,836,363 Dated p b r 17, 197MInventofls) Thomas Miles Plutchak It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 3, line 8, the word "extend" should read --eXtent--.

Column 6, line 23, the word "floor" should read ----flood--;

and online 2 1, after "red" the word --light--should be added.

Column 8,' line 6 the word "blank" should read -black--.

Column 13, line 16, the word "electrophotoconductive'" after "color"should read -e1ectrophotogr'aphic-.

Signed and sealed this 8th day of April 1975.

(SEAL) fittest: C. MARSHALL DANN RUTH C. MAS-ON Commissioner of PatentsAttesting Officer and Trademarks

2. The process according to claim 1 wherein some of the filter elementsof the mosaic layer of the recording element are predominantlytransparent to a third additive color and wherein the exposure sourceused in the imagewise exposing step further comprises light of the thirdadditive color to which the mosaic layer is transparent, and saidprocess further comprises the steps of: j. uniformly charging the secondphotoconductive layer bearing the superimposed second and third tonerimages; k. exposing the second photoconductive layer to light of saidthird additive color, such exposure being effected through the firsttoner image borne by the surface of the first photoconductive layer andthrough the mosaic, thereby selectively dissipating the uniform chargeon the second photoconductive layer in those areas opposite thoseilluminated filter elements of the mosaic layer which are predominantlytransparent to said third additive color to form a fourth electrostaticimage which is superimposed on the second and third toner images; and l.selectively applying a fourth electroscopic toner to the fourthelectrostatic image to produce a third toner image on that surface ofthe second photoconductive layer bearing the superimposed second andthird toner images, such fourth electroscopic toner being of a colorwhich is predominantly spectrally absorptive of the third additivecolor, whereby a multicolored image is formed of the color original,such multicolored image being comprised of the superimposed second,third, and fourth toner images.
 3. The process according to claim 1further comprising the step of transferring the toner image to areceiving member.
 4. The process according to claim 2 wherein the first,second, and third additive colors are red, green, and blue; and thecolors of the electroscopic toners which are applied following the red,green, and blue flood exposures are cyan, magenta, and yellow,respectively.
 5. The process according to claim 4 wherein the first,second, third, and fourth toners are applied to those areas on thephotoconductive surfaces where charge is dissipated during the exposuresteps.
 6. The process according to claim 4 wherein the first, second,third, and fourth toners are applied to those areas on thephotoconductive surfaces where electrostatic charge remains after theexposure steps.
 7. The process according to claim 4 wherein the firsttoner is applied to those areas on the first photoconductive layer wherecharge is dissipated during the imagewise exposure step and wherein thesecond, third and fourth toners are applied to those areas on the secondphotoconductive layer where charge remains after the subsequent exposuresteps, whereby a negative multicolored image is provided on the secondphotoconductive layer.
 8. The process according to claim 4 wherein thefirst toner is applied to those areas on the first photoconductive layerwhere charge remains after the imagewise exposure step and wherein thesecond, third and fourth toners are applied to those areas on the secondphotoconductive layer where charge is dissipated during the subsequentexposure steps, whereby a negative multicolored image is provided on thesecond photoconductive layer.
 9. The process according to claim 4wherein the first photoconductive layer is uniformly charged to onepolarity prior to being imagewise exposed to the multicolored originaland the second photoconductive layer is uniformly charged to an oppositepolarity each time prior to being subsequently exposed.
 10. A processfor producing a multicolored image from a multicolored original using arecording element comprising (a) a first pan-sensitive photoconductiVelayer having an optically transparent, electrically conductive layer inelectrical contact with one surface thereof, (b) a second pan-sensitivephotoconductive layer having an optically transparent, electricallyconductive layer in electrical contact with one surface thereof, and (c)a trichromatic additive colored mosaic comprising red, green, and bluefilter elements positioned between the conductive layers of the firstand second photoconductive layers, said process comprising the steps of:a. uniformly charging the first photoconductive layer of the recordingelement; b. imagewise exposing the first photoconductive layer to themulticolored original, such imagewise exposure being effected throughthe multicolored mosaic using an exposure source comprising a mixture ofred, green, and blue light, thereby forming a first electrostatic imageon the first photoconductive layer in accordance with the image of themulticolored original; c. selectively applying an opaque electroscopictoner to the first electrostatic image-bearing surface of the firstphotoconductive layer to produce an opaque toner image; d. successivelyuniformly charging, exposing, and applying toner particles to the secondphotoconductive layer using red, green, and blue light to exposefollowed by the application of cyan, magenta, and yellow coloredelectroscopic toner, respectively, such exposures to red, green and bluelight being made through the opaque toner image and the multicoloredmosaic.
 11. A color electrophotographic recording element comprising: a.first and second optically transparent, pan-sensitive photoconductivelayers, each having an optically-transparent conductive layerelectrically associated therewith; and b. a trichromatic additivemulticolored mosaic comprising red, green, and blue filter elementsdisposed between the conductive layers of the first and secondphotoconductive layers.
 12. A separable color electrophotoconductiverecording element comprising: a. a first optically transparent,pan-sensitive photoconductive layer having an optically transparentelectrode in electrical contact with one surface thereof; b. a secondpan-sensitive photoconductive layer having an optically transparentelectrode in electrical contact with one surface thereof; and c. amulticolor additive filter mosaic layer disposed between the electrodesof the first and second photoconductive layers.
 13. A process forproducing a multicolored image from a multicolored original using amulti-layered recording element comprising first and secondpan-sensitive, photoconductive layers, each having an opticallytransparent, electrically conductive layer in electrical contact withone surface thereof; and a multicolored filter mosaic disposed betweensuch conductive layers, the conductive layers and the photoconductivelayers being optically transparent, and the multicolored mosaic beingdivided into a multitude of color filter elements, some of such filterelements being predominantly transparent to a first additive color, andothers being predominantly transparent to a second additive color, saidprocess comprising the steps of: a. uniformly charging the firstphotoconductive layer of the recording element; b. imagewise exposingthe first photoconductive layer to the multicolored original, suchimagewise exposure being effected through the mosaic and the secondphotoconductive layer using an exposure source comprising light of atleast said first and second additive colors, thereby forming a firstelectrostatic image on the first photoconductive layer in accordancewith the image of the multicolored original as attenuated by the mosaic;c. applying a first electroscopic toner to the first electrostatic imageto produce a first toner image on a surface of the first photoconductivelayer, such first electroscopic toner being opaque to the first andsecond additive colors to which the mosaic is transparent; d. uniformlycharging the second photoconductive layer; e. exposing the secondphotoconductive layer to light of said first additive color, suchexposure being effected through the first toner image borne by thesurface of the first photoconductive layer and through the mosaic,thereby selectively dissipating the uniform charge on the secondphotoconductive layer in those areas opposite those illuminated filterelements of the mosaic which are predominantly transparent to the firstadditive color to form a second electrostatic image; f. applying asecond elecroscopic toner to the second electrostatic image to produce asecond toner image on a surface of the second photoconductive layer,such second electroscopic toner being of a color which is predominantlyspectrally absorptive of said first additive color; g. uniformlycharging that surface of the second photoconductive layer bearing thesecond toner image; h. exposing the second photoconductive layer tolight of said second additive color, such exposure being effectedthrough the first toner image borne by the surface of the firstphotoconductive layer and through the mosaic, thereby selectivelydissipating the uniform charge on the second photoconductive layer inthose areas opposite those illuminated filter elements of the mosaicwhich are predominantly transparent to the second additive color to forma third electrostatic image which is superimposed on the second tonerimage; and i. applying a third electroscopic toner to the thirdelectrostatic image to produce a third toner image on that surface ofthe second photoconductive layer bearing the second toner image, suchthird electroscopic toner being of a color which is predominantlyspectrally absorptive of said second additive color, whereby amulticolored image is formed of the color original, such color imagecomprising the superimposed second and third toner images.
 14. A processfor producing a multicolored image from a multicolored original using aseparable recording element comprising (a) a first pan-sensitive,optically transparent photoconductive layer having an electricallyconductive, optically transparent layer in electrical contact with onesurface thereof, (b) a second pan-sensitive photoconductive layer havingan electrically conductive, optically transparent layer in electricalcontact with one surface thereof, and (c) a multicolored mosaic dividedinto a multitude of color filter elements, some of such filter elementsbeing predominantly transparent to a first additive color, and othersbeing predominantly transparent to a second additive color, said processcomprising the steps of: a. uniformly charging the first photoconductivelayer of the recording element; b. imagewise exposing the firstphotoconductive layer to the multicolored original, such imagewiseexposure being effected through the mosaic using an exposure sourcecomprising light of at least said first and second additive colors,thereby forming a first electrostatic image on the first photoconductivelayer in accordance with the image of the multicolored original asattenuated by the mosaic; c. applying a first electroscopic toner to thefirst electroscopic image to produce a first toner image on a surface ofthe first photoconductive layer, such first electroscopic toner beingopaque to the first and second additive colors to which the mosaic istransparent; d. uniformly charging the second photoconductive layer; e.exposing the second photoconductive layer to light of said firstadditive color, such exposure being effected through the first tonerimage borne by the surface of the first photoconductive layer andthrough the mosaic, thereby selectively dissipating the uniform chargeon the second photoconductive layer in those areas opposite thoseilluminated filter elements of the mosaic which are predominantlytransparent to the first additive color to form a second electrostaticimage; f. applying a second electroscopic toner to the secondelectrostatic image to proDuce a second toner image on a surface of thesecond photoconductive layer, such second electroscopic toner being of acolor which is predominantly spectrally absorptive of said firstadditive color; g. uniformly charging that surface of the secondphotoconductive layer bearing the second toner image; h. exposing thesecond photoconductive layer to light of said second additive color,such exposure being effected through the first toner image borne by thesurface of the first photoconductive layer and through the mosaic,thereby selectively dissipating the uniform charge on the secondphotoconductive layer in those areas opposite those illuminated filterelements of the mosaic which are predominantly transparent to the secondadditive color to form a third electrostatic image which is superimposedon the second toner image; and i. applying a third electrostatic tonerto the third electrostatic image to produce a third toner image on thatsurface of the second photoconductive layer bearing the second tonerimage, such third electroscopic toner being of a color which ispredominantly spectrally absorptive of said second additive color,whereby a multicolored image is formed of the color original, such colorimage comprising the superimposed second and third toner images.